1. Field of the Invention
The present invention relates to a camera with a control apparatus for charging a storage capacitor for a flash light emission. More specifically, the present invention relates to a camera having a control apparatus for charging a storage capacitor for a flash light emission controlling a charging state indicator.
2. Description of Related Art
U.S. Pat. No. 4,628,229 discloses a control apparatus for charging a storage capacitor for flash light emission including a boosting circuit for boosting battery voltage, a capacitor which is charged with the output from the booster circuit, indicating means for indicating the state of charging of the capacitor during the operation of the boosting circuit, means for detecting voltage of the capacitor and means for stopping the operation of the boosting circuit when the voltage of the capacitor reaches a prescribed voltage. In this prior art, the indicating means indicates that the charging is being carried out whenever the charging of the capacitor is carried out by the boosting circuit.
If the indication of the charging state is always carried out while the capacitor is being charged, power is consumed for the indication, and there may be unnecessary power consumption. A method for preventing such unnecessary power consumption is disclosed in, for example, Japanese Patent Laying-Open Gazette No. 62145/1985. According to this gazette, indication of the completion of charging is carried out for only a prescribed time period after the fully charged state of the capacitor is detected in a control apparatus for charging a storage capacitor for a flash light emission.
Another method for preventing power consumption in association with the indication of fully charged state is disclosed in, for example, U.S. Pat. No. 4,630,916. According to this patent, a control apparatus for controlling charging of a storage capacitor for flash light emission comprises a timer and the state of charging of the capacitor is checked periodically in accordance with the measurement by the timer.
As described above, conventionally, indication in association with the state of charging is sometimes limited in consideration of reduction power consumption.
Now, electric flash is automatically emitted when low brightness is detected or when rear light is detected in cameras incorporating electric flash, which are popular recently. Therefore, the frequency of electric flash emission has been increased. Further, in a control circuit of the camera, whether the emission of electric flash is necessary or not for the next photographing operation cannot be determined until the brightness of a subject is measured while a shutter button is kept at the first stroke. Consequently, the capacitor for emitting electrical flash must be always kept at the fully charged state in order to minimize a release time lag caused by the charging of the electric flash.
For this purpose, if the capacitor for emitting electric flash is not fully charged, then charging must be started at the time when a lens barrier is changed from closed state to open state, when photographing operation with flash light emission is completed, when low brightness is detected, when rear light is detected and when a switch for forcing emission of electric flash is operated. At that time, indication of "charging is being carried out" is provided indicating whether or not photographing operation with flash light emission can be carried out, so that the user can determine the states of the camera.
Sometimes charging of the capacitor for emitting electric flash is started after a photographing operation without using the electric flash. If the "charging" indication is provided in such a case, the user is informed of the fact that the charging is started for flash light emission even though he did not use the electric flash. Consequently, the user may become anxious for the operation of the camera or he may have a complaint about the power consumption of the camera
In addition, the time required for charging for the flash light emission has become very short recently, so that the time for charging is not an obstacle in the photographing operation in most cases If the voltage of the capacitor for emitting electric flash is slightly lower than the level allowing emission of flash, that level can be soon reached after the start of the charging operation. In such case, if the indication of charging state is provided after the start of the charging operation until the level allowing emission of flash is reached, then the user may stop photographing operation, being conscious of the fact that the camera is not fully charged.
Consequently, good chances for photographing may be missed. In most cameras, releasing operation is locked even if the shutter button is pressed when the capacitor for flash light emission is not fully charged. Therefore, the shutter button must be pressed again for releasing. In such cameras, repressing of the shutter button is needed because of the small time period for charging, which time is not essentially an obstacle in the photographing operation. Good chances for taking photographs may be missed in such cases also.